Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the readOnly/openWorld annotations, it discloses the comparison's data source limitation (archive-only), the 404 failure mode for unarchived pages, and the full pricing model including that failed calls are free. These are exactly the operational traits an agent needs before spending a paid call.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Well front-loaded: what it does first, then the archive constraint and 404 case, then pricing. Three sentences each carry distinct information; minor verbosity in the price-currency enumeration but nothing wasteful.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Output schema covers return values, annotations cover safety, and the description fills the remaining gaps an agent needs: comparison scope, failure mode, and cost. Nothing material is missing for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so url and since are already documented including the 30-day default. The description adds the 'on or after a date' semantic for the baseline snapshot, but that is a modest increment over the schema and not enough to exceed the baseline.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (compares) and clearly defined resources (a public page now vs. its earliest Wayback snapshot on or after a date), then enumerates the exact outputs (changed flag, word similarity, added/removed lines, price-like amounts). No sibling tool does page-diffing, so the agent can distinguish it unambiguously.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a clear usage boundary: 'Only what the archive captured is compared; pages the archive never saved return 404,' which tells the agent when the tool will fail. It does not name an alternative tool, so it stops short of full when-not/alternatives guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.